Radon in Connecticut
About 3 in 10 homes tested in Connecticut were at or above the EPA action level of 4 pCi/L.
- Below 2 pCi/L: 50%
- 2 to 4 pCi/L: 24%
- 4 pCi/L or more: 26%
The EPA puts 4 of Connecticut's 8 counties in Zone 1, its highest radon category, 3 in Zone 2 and 1 in Zone 3.
Every county in Connecticut
Sorted by the share of homes tested at or above 4 pCi/L. Select a county for local details and costs.
| County | Homes tested | At or above 4 | Median | EPA zone |
|---|---|---|---|---|
| Windham County | 34% | 2.6 pCi/L | 2 | |
| Middlesex County | 31% | 2.2 pCi/L | 1 | |
| Litchfield County | 29% | 2.0 pCi/L | 2 | |
| New London County | 28% | 2.1 pCi/L | 1 | |
| Fairfield County | 27% | 2.1 pCi/L | 1 | |
| Tolland County | 27% | 2.2 pCi/L | 2 | |
| New Haven County | 26% | 1.8 pCi/L | 1 | |
| Hartford County | 21% | 1.5 pCi/L | 3 |
"–" means fewer than 20 tests or no lab data, too few for a reliable figure.
Sources
- EPA Map of Radon Zones (public domain).
- CDC Environmental Public Health Tracking Network, radon tests from labs, 2008–2017. Pre-mitigation tests only.
Last updated October 2026. How we calculate these numbers.